1. Field of the Invention
The present invention relates to image forming apparatuses and computer program products.
2. Description of the Related Art
Inkjet recording apparatuses have become widespread for personal use because of their inexpensive pricing and high image quality of printouts produced using special paper. Inkjet recording apparatuses have steadily come into widespread use also in offices as recording apparatuses capable of color printing.
Improving recording speed has been desired to achieve wider spread of inkjet recording apparatuses in offices. More specifically, a typical inkjet recording apparatus performs recording by ejecting ink onto a recording sheet from a print head, which is considerably small as compared with the recording sheet, that repeatedly runs across a surface of a recording sheet. This can be said to be a recording scheme that performs recording on a “line-by-line” basis. This scheme is considered to be less advantageous in terms of recording speed than laser printers and the like that perform recording on a per-page basis, or, put another way, on a “sheet-by-sheet” basis.
Under the circumstances, improvements have been made on inkjet recording apparatuses to resolve the disadvantage in terms of speed. Examples of the improvements include shortening a cycle period of ink ejection to thereby increase a scan speed, reducing the number of scans by increasing the size of a recording head or employing bi-directional recording, and increasing efficiency of a scan sequence by adopting minimum-scan control of scanning only portions where image data is to be recorded.
However, unlike laser printers, off-set printing, and the like that cause a coloring material to fix onto the surface of a sheet, inkjet recording apparatuses cause a coloring material to permeate into a sheet and then fix thereto. For this reason, a problem and/or restriction associated with a penetration process are inherent to inkjet recording apparatuses.
For example, inkjet recording apparatuses have a problem resulting from that ink sticking to a sheet at one spot earlier is likely to yield more intense color than ink sticking to the same spot later does. More specifically, an ink impacting order is generally reversed in a bi-directional printing mode that increases a print speed. However, this reversing can undesirably cause a thin, horizontal banding pattern to be formed because color of each scanning band printed by a forward stroke differs from that printed by a backward stroke, and hence result in degradation in image quality.
Techniques have been proposed as countermeasures against a color difference resulting from different ink impacting orders such as a color difference that develops during bi-directional recording (hereinafter, referred to as “bi-directional color difference”). One of the techniques is disclosed in Japanese Examined Patent Application Publication No. H03-545082. The technique disclosed in Japanese Examined Patent Application Publication No. H03-545082 prevents difference between colors recorded by a forward stroke and colors recorded by a backward stroke by causing color conversion process for forward stroke scanning to differ from that for backward stroke scanning.
However, the technique such as that disclosed in Japanese Examined Patent Application Publication No. H03-545082 that simply switches between a color conversion process for forward stroke scanning and that for backward stroke scanning disadvantageously requires additional cost to increase capacity of buffer memory or the like when it is necessary to hold image-processed data until printing is performed. This disadvantage becomes more serious in wide format inkjet recording apparatuses (wide format printers).
Therefore, there is a need for an image forming apparatus capable of outputting printouts in appropriate hue without sacrificing print speed and with reduced additional cost.